Archive for October, 2010

Famously, this fall, Sockeye Salmon have returned to spawn in unexpectedly large numbers in the Fraser River system in southern British Columbia. This is after several years of such unexpectedly low returning numbers that commercial fishing ceased. We clearly don’t understand what’s happening, except that we know the predictive models have failed.

Sockeye salmon turn red and hook-nosed as they migrate up river (cybersalmon.fws.gov)

All five Pacific salmon species grow to adulthood in the Gulf of Alaska. Sockeye have the largest range. (ats.agr.gc.ca)

Actually, after two and a half years growing to adults in the North Pacific, Sockeye have returned in colossal numbers, 35 million of them – the most in a century – to breed in the inland tributaries of the Fraser River, many swimming for 17 days 480 km up to the 12 km of the Adams River where they spawn in the shallows, and then die.

Sockeye migrating up the Fraser River (conserv.org)

For a long time, every fourth year the number of returning salmon has been particularly great, celebrated by the quadrennial mid-October festival ‘Salute to the Sockeye’. When a large number spawn, four years later their offspring should return in large numbers. If a small number spawn, four years later the run ought to be small as well.

This year 150,000 tourists have come to Salute the Sockeye run in the Adams River. (tripatlas.com)

In fact, in 2006, only 1.5 million fish returned to the mouth of the Fraser. In 2007 only 1.4 million returned, and fishing for them was radically curtailed. In 2008, 1.6 million returned, and the species was ‘red listed’ by the IUCN, identified as threatened. In 2009, when 11 million were expected, only 1.5 million showed up, and everyone agreed a fishery collapse had occurred.

Why so few? Was this the end of the fishery? A Canadian federal inquiry is trying to understand the causes of the collapse, assessing the roles of ocean warming, overfishing, diseases, pollution, sea lice infections, government fisheries policies, and food shortages in the Pacific. A challenge, to say the least.

The Fraser River basin is immense. Sockeye breed in many of its tributaries, but the Adams River population is the msot famous (nanaimo-info-blog.com)

Some evidence suggests the fish die not long after swimming the gauntlet of 70 possible contaminating fish farms as they head north from the Fraser River as juvenile. And yet the 35 million fish that returned in 2010 also had to swim the same gauntlet of 70 fish farms when they were juveniles. How do we account for that success?

Years of terminally low runs, now the largest run in a century. What on earth is going on?

A recent suggestion is that, when the Alaskan Kasotochi volcano erupted in 2008, it fertilized the Gulf of Alaska with iron rich ash which then supported an explosion of plankton over an area 1000 km wide. This year’s returning Sockeye population would have been there at the peak of the bloom, feeding heavily and growing rapidly. In other words, a one-off event.

Kasatochi Volcano erupted in August 2008, spewing ash westward over the Gulf of Alaska (superorganicfoods.com)

Whatever the causes, we now have the image of a spectacular run despite all the other horrible things going on in the ocean’s ecosystems, indicating that recovery of wild Sockeye salmon populations is at least possible – possible perhaps by protecting, nourishing, and increasing the productivity of the Gulf of Alaska. Another huge challenge.

There is alway potentially immense and unpredictable variation in the size of any fish population, even under what we think are relatively stable environmental conditions. Adding then the changes that are occurring in the oceans as a result of ocean warming, overfishing, and contamination, predictability becomes increasingly unlikely. How do you make predictions when the rules are changing in unpredictable ways?

Can we say with certainty what lies ahead for us?
Of course we can: increasing unpredictability.

Grizzly charges to catch a sockeye. Or perhaps a tourist. (alaskaalpinetreks.com)

There’s a new fish in town. Well, perhaps not that new, since Oprah featured it in her magazine, and Paul Greenberg included a few pages on it in his fine book Four Fish. But it’s new for me, and perhaps it is for you as well.

It’s a kind of seabass called Barramundi, an Australian Aboriginal word that means ‘large-scaled river fish’. It lives along the coasts and estuaries of South West Asia, Papua New Guinea, and Northern Australia. Some call it Asian Seabass. The Thai call it Pla Krapong, and eat a lot of it.

The seabass Barramundi (Lates calcarifer), with its large silver scales (reef.crc.org.au)

This is a fish worth seeking out at your local fish market. Like other coastal seabass, it is a white fish that is considered to be fine eating. Like other seabass, it is also an exciting recreational fish – it grows large and fights hard, and supports an active recreational fishery, at least in Northern Australia and in Thailand – but that’s another story.

Most seabass grow up in coastal waters and then migrate up coastal estuaries to breed. Barramundi do the opposite: they live in rivers, and then descend to estuaries and tidal flats to breed. A female lays millions of eggs that require at least brackish water to develop. The fish grow up as males, reaching a length of about 60cm by the time they are 3 years old, and then they become females as they continue to grow. This is an excellent reproductive strategy – males don’t need to be large to produce abundant sperm, while the larger a female, the more eggs she can produce. A female could grow to 1.8 m in length, and then shed a remarkable 30 million eggs.

The unusual life cycle of Barramundi (hinchinbrookfishing.com.au)

This is a fish that is ideal for aquaculture. It has huge gills that let it tolerate environments with little oxygen. It is disease resistant, needing little in the way of antibiotics, or hormone supplements, for that matter. Despite its reputation as a spectacular fighting sport fish, it is docile in captivity. And it grows quickly on vegetarian feed, able to make Omega-3 from plant oils. It needs only small amount of fish oil and feed at end, as a finishing diet. It is usually sold at about 400gm and 32cm ‘plate size’, good for 2 people.

A small, spiced Barramundi cooked on a banana leaf (smh.com.au)

Most Barramundi aquaculture of course is in Australia, India, Indonesia, and Thailand, though Israel and Poland are in the business as well. In the US, it is cultured at Australis Aquaculture at Turners Falls, Mass, in a closed, recirculating system using water from the Connecticut River. They start with hatchery fish at least 5cm long, grow them to 400-600gm in 12 months, and to 3kg in 18-48 months.

So: fast growing, and unlike salmon, mostly vegetarian, non-polluting, disease resistant, and no added antibiotics or hormones. This fish could solve a lot of aquaculture challenges. And yes, it has a fine flaky white flesh. Steam it, fry it, or grill it wrapped, with some herbs, lemon, and white wine.

Lemon and herbs, Barramundi: too good. (thebetterfish.com)

I found Barramundi at a fish monger in the great St.Lawrence Market in Toronto, but it isn’t always there. I don’t see it around at the local supermarkets, but I’m asking every time I visit.